Draftsman{3 s aid for preparing axonometric drawings and projections

ABSTRACT

A draftsman&#39;&#39;s aid for preparing axonometric drawings and projections having a primary article representing the frontal and profile planes and equipped with a pair of protractors, and adapted to be used with a secondary triangular shaped article representing the horizontal plane, is disclosed.

United States Patent Whitt Aug. 5, 1975 [5 DRAFISMANS AID FOR PREPARING655,005 7/1900 Penfield 33/75 R AXONOMETRIC DRAWINGS AND :8: PROJECTIONS3:358:9l6 10/1966 Suto Q: .11. 33/77 [76] Inventor: Minton E. Whitt,P.O. Box 558,

Farmers, Ky. 403 l9 [22] Filed: Jan. 4, 1974 [21] Appl. No.: 430,722

[52] US. Cl. 33/77; 33/75 R [5i] lnt. Cl. B43L 13/14 [58] Field ofSearch 33/75 R, 75 A. 75 B, 77

[56] References Cited UNITED STATES PATENTS 262,137 8/1882 Silliman33/77 Primary E.raminerRichard E. Aegerter Assistant Examiner-Michael H.Thaler Attorney, Agent, or Firm-William E. Sherwood [5 7] ABSTRACT Adraftsmans aid for preparing axonometric drawings and projections havinga primary article representing the frontal and profile planes andequipped with a pair of protractors, and adapted to be used with asecondary triangular shaped article representing the horizontal plane,is disclosed.

5 Claims, 7 Drawing Figures PATENTEDAUB "51975 3,897, 633 SHEET 1 FIG. 3

OIIIII o l l F|G.I

DRAFTSMANS AID FOR PREPARING AXONOMETRIC DRAWINGS AND PROJECTIONSBACKGROUND OF THE INVENTION The construction of axonometric drawings andprojections, particularly of the dimetric and trimetric types, arelaborious and time-consuming, and many forms of aids for the draftsmanhave been proposed to assist him in this task. However, such aidsusually are unduly complicated and expensive and often do not materiallysimplify the work of the draftsman. It is a purpose of the presentinvention to overcome these and other disadvantages of conventionalarticles used in the making of such drawings and projections.

By definition, drawings or projections of the simpler isometric typehave each of the X, Y and Z axes 120 apart and these axes representingthe width, height and depth of object to be depicted remain in the sameproportional ratios. On the other hand, dimetric drawings or projectionsare more difficult to construct in that two of the three axes make equalangles of more than 90 with the plane of projection and with the thirdaxis at a different angle, thus permitting only two of the threedimensions to have the same proportional ratio.

Finally, the most difficult drawing or projection to construct is thetrimetric type in which all three axes make unequal angles with theplane of projection and wherein each axis must be developed separatelysince no two of the three axes have the same proportional ratio.

During the construction of an axonometric drawing little or noconsideration is given to the degree of foreshortening whereas inconstructing an axonometric projection the object being constructed notonly is placed in proper relationship to the plane of projection, butalso embodies the correct degree of foreshortening along each of itsthree axes. As will later appear, the present invention provides a meanswhereby the draftsman may construct any of these three types of drawingsand projections in an accurate and relatively simple manner ascontrasted with present practices.

SUMMARY The invention comprises a draftsmans aid including a primaryarticle with which axonometric drawings may be made, and a supplementarytriangular article which when used in conjunction with the primaryarticle enables the draftsman to make axonometric projections. Theprimary article includes right and left protractors pivotally mounted onarms extending from a flat frame member which has a straight lower edgeadapted to be referenced against a T-square or the like, and theprotractors move in the plane of the flat member. At least one of theprotractors is provided with an array of holes through which markingsrepresentative of the setting of the protractor can be made upon anunderlying worksheet. The supplementary article includes scales alongedges representative of X-axis and Z-axis readings and with arrays ofholes along those scales.

Among the objects of the invention are the provision of an improved,simple, and inexpensive draftsmans aid for making axonometric drawingsin a less laborious and more accurate manner; the provision of adraftsmans aid consisting of separate primary and secondary articleswhich cooperate in the making of axonometric projections; the provisionof a draftsman's aid by means of which the teaching of the principles ofmechanical drawing for complex showings of objects may be simplified;and the provision of a draftsmans aid which permits the production ofaxonometric projections in a shorter time than heretofore possible.

These and other objects and advantages of the invention will become moreapparent as the description proceeds and when considered in conjunctionwith the accompanying drawings in which FIG. 1 is a plan view of theprimary article to be employed by the draftsman.

FIG. 2 is a plan view of the secondary article to be employed with theprimary article when constructing trimetric projections.

FIG. 3 is a sectional view to an enlarged scale taken on line 3-3 ofFIG. I.

FIG. 4 is an isometric drawing of an object as constructed with theprimary article.

FIG. 5 is a dimetric drawing of an object as constructed with theprimary article.

FIG. 6 is a trimetric drawing of an object as constructed with theprimary article of the invention; and

FIG. 7 is a preferred geometrical and graphical construction of atrimetric projection as developed by use of the primary and secondaryarticles of the invention.

Referring now to FIG. I, the primary article comprises a flat framemember 10 preferably constructed of rigid transparent plastic materialand having a straight lower edge II adapted to rest against the usualT-square or other reference means employed in drafting work. Rigid rightand left arms 12 and I3 respectively are attached as by bonding to theupper surface of the member and provide pivotal supports 14, 15 for apair of protractors l6, 17 respectively. The frame member is cut awaybeneath these supports and is shaped to provide for movement of theprotractors in the plane of the member. Moreover, the central portion ofthe member is formed with an open notch having symmetrical straightedges 18 and 19 respectively representing the X-axis and Z-axisdirections for certain drawings made by means of the primary article.These edges intersect at point 20 from which a visible line 21 on thesurface of the frame member extends normally toward the long edge I] andrepresents the Y-axis.

Theoretically, axonometric drawings and projections are graphicrepresentations of resulting positions of objects which have beenrevolved and tilted with respect to the plane of projection. The topedges 22 and 23 of the right and left arms are on a common line parallelto the lower edge 11 and represent the plane of projection while theright hand edge 24 of arm 12 is perpendicular thereto and represents theprofile plane; the flat body 10 of the primary article meanwhilerepresenting the frontal plane. The protractors are movable to provideselected settings, for example between 0 and 1 5 and between 0 and andby means of suitable thumb screws 25, 26 mounted in the arms may be heldin the selected position following the setting of the protractor.

The right hand protractor which serves the dual purpose of determiningthe angle at which the Z-axis (depth dimension) recedes (slopes) fromthe plane of projection, and of determining the tilt angle for theprofile plane, is provided with a scale 27 on its top straight edge andwith an open slot 28 with accompanying scale 29 for measuring along theintended Y-axis. This scale 29 employs a zero mark which lies on theline extending from pivot 14 to the 90 mark on the quadrant scale ofprotractor 16. Various profile tilt angles depending upon the selectedadjustment made on the right frontal protractor 16 may be drawn directlyon the worksheet by a pencil moving in this slot. A series of holes inthe protractor adjacent this scale provides for the making of referencepoints on the worksheet by means of a pencil point or the like insertedthrough these holes and with each such point being uniformly related tothe Y-axis angle of the slot. As will later appear, these points areused for drawing lines to help in establishing foreshortening of theobject.

The left hand protractor serves three purposes, namely; to determine theangle at which the X-axis (width dimension) recedes from the plane ofprojection; to measure true heights on the Y-axis; and to provide asupport for the secondary article when developing axonometricprojections. This protractor has a scale along its straight top edge andalso a vertical scale 36 along its leftmost edge which is normal to thattop edge.

The scales (normally subdivided into degrees) along the quadrant portionof both protractors are read at points where such scales revolve beneaththe inner edges of the respective upright arms 12 and 13 and, ifdesired. supplementary vernier scales 37, 38 (subdivided into minutes)may be mounted upon the respective arms in order to provide for moreprecise settings. Moreover the arms 12 and 13 may be recessed as shownat 37A and 38A to make visible scale portions on the protractorsrepresenting settings thereof employed in making perspective drawings,as when the straight top edges of the protractors are revolved in areverse direction. As later to be explained, in the making of certainprojections it is important to position the primary article at an exactpoint beneath the pivotal axis of the protractor and as seen in FIG. 3 ahollow ferrule 40 pinning the protractor to the arm and containing amagnifying glass insert 41 with a pair of cross hairs thereon may beemployed.

For use with the above described primary article the secondary articleshown in FIG. 2 is employed in the making of projections and comprises aflat transparent triangular member representing the horizontal plane.This member is formed with one straight edge 45 having a scale 46 forX-axis readings and a series of holes 47 for establishing points on thework sheet along that X-axis. In addition one straight edge 48 having ascale 49 for Z-axis readings and with a series of holes 50 forestablishing points on the work sheet along that Z-axis is provided; theedges 45 and 48 intersecting at a right angle and with a visible line 51representing the Y-axis being present on the surface and bisecting theright angle.

EXAMPLES OF USAGE OF THE AID Considering now the preparation ofatrimetric drawing as seen in FIG. 6 with angles as indicated; thedraftsman first sets the left frontal protractor 17 to 0 and then drawsthe Y-axis line of the intended object to the selected scale by means ofthe scaled left edge 36 of the primary article. Then he adjusts theprotractor 17 to a 25 setting and draws X-axis line 61 from the upperend of line 60 using the scale edge 35 for direction and scalingpurposes and leaving the protractor 17 at its 25 setting. Then headjusts the right frontal protractor 16 to a 35 setting and using thescale edge 27 draws a Z-axis line 62 from the upper end of line 60,leaving protractor 16 at its 35 setting.

Thereafter he shifts the primary aid with its protractors locked at theabove settings to draw the lower X- axis line 63 followed by shifting ofthe primary aid to draw the lower Zaxis line 64. Further shifting of theprimary aid allows the drawing of the distant X-axis line 65 and thedistant Z-axis line 66. After this, the left frontal protractor isrestored to its 0 setting and its left vertical scale edge 36 is used tocomplete the drawing by means of the left Y-axis line 67 and the rightY-axis line 68. As will be seen, this trimetric drawing of a cube hasbeen made merely by using the straight lower edge 11 resting against areference surface such as an adjustable T-square; (b) the left scaleedge 36; (c) the upper scale edge 35 of one protractor; (d) the upperscale edge 27 of the other protractor and (e) the quadrant scales ofboth protractors.

By contrast, the preparation of a trimetric projection of the cube ofFIG. 6 (with foreshortening, tilting, and revolving) involves use ofboth the primary and secondary articles of the draftsmans aid. Referringnow to the construction shown in FIG. 7 the draftsman sets bothprotractors at 0 and draws the straight horizontal line 70 representingthe plane of projection (P.O.P.) line and after shifting the primary aidthen draws the vertical line 71 (the Y-axis line of the drawing) bymeans of the scale edge 36 of the left protractor. The thumb screw 25 isthen loosened and the right protractor is revolved 45 out of the way.The thumb screw 26 is then loosened and the left protractor 17 (whichnow acts as the horizontal protractor) is revolved to the desired angleof revolution of the top view of the intended object after which thumbscrew 26 is tightened. The primary article is then shifted with its line21 coinciding with line 71 on the drawing sheet and using the scale edge35 an inclined line 72 is drawn. This line intersects the POP. line at Xand the Y-axis at 0.

Now using the secondary article with its X-axis edge coinciding withline 72 and its apex at 0, a line 73 is drawn to intersect with theP.O.P. line at Z.

The left protractor of the primary article being reset to 0 is then usedto draw a laterally displaced vertical construction line 74 downwardlyfrom point A on the POP. line. Also a line 75 parallel to the POP. linefrom point 0 to the point B of intersection with line 74 and extendingtherefrom a suitable distance is drawn using the lower edge 11 of theaid.

The right protractor I6 is then set to and the primary article is laidupon the work sheet with the cross hair of the insert 41 at the pivotsupport 14 coinciding with point A and with its lower edge 11 beingparallel with line 75. A reading is then taken on the right protractorcorresponding to where line 75 extended intersects quadrant scale of theprotractor, and this reading is jotted down by the draftsman.

Keeping the primary article in the same position as when the reading istaken, rotate the right protractor to the desired tilt angle of theobject to be depicted, for example 35, lock the thumb screw 25 and witha pencil make a dot C on the work sheet corresponding to a reading ofthe scale on the quadrant of the protractor which is the same as thereading earlier jotted down. Then draw the line 76 from dot C to point Ausing the scale edge 27 of the protractor and thereafter shift theprimary article while still locked at its 35 setting and with its loweredge 11 still parallel to line 75 to bring the scale side 29 of the slot28 into alignment with dot C.

A line 77 is then drawn from dot C by means of a pencil moving in theslot and this line is extended to intersect with line 74 at point D. Ascaled series of dots 99 are then made on the work sheet by inserting apencil point through the holes 30 adjacent the slot in the protractor. Aline 78 is then drawn from dot C horizontally parallel to line 75 tointersect with line 71 at point Y which establishes the initial point inthe front view showing of the object to be depicted. Following this aseries of parallel lines 100 which are parallel to line 78 are drawn totheir intersection with the Y-axis line 71 whereupon the true shape andsize of the height of the foreshortened front vertical Y-axis edge ofthe cube (as it would appear to an observer looking into the frontalplane in a perpendicular manner) is established along line 71.Thereafter using any straight edge lines 79 and 80 are drawnrespectively from point Y to points X and Z whereupon the space boundedby lines 70, 80 and 79 represents the front view of the object after ithas been tilted and projected from the profile view, or in other wordsthese three lines are the lines which the cube makes with the frontalplane of projection.

From point D using a straight edge a construction line 81 is drawnparallel to line 75 to intersection with the Y-axis line 71 at point Eand lines 82 and 83 are drawn respectively to points X and 2 from pointE.

Lines 79 and 80 are then extended a suitable distance as lines 79A and80A respectively and using the secondary triangular article with itsapex lying upon line 79A and its X-axis and Z axis edges touching pointsE and Z respectively, lines 84 and 85 are drawn from the apex to pointsE and Z respectively. Then with the triangular article held with itsline of holes 50 over line 85 a series of scaled dots 86 are madethrough those holes. Using a straight edge a series of parallel lines 87which are parallel to line 79A are drawn to their intersections withline 80 thus depicting the upper Z-axis edge of the cube in the desiredforeshortened size.

In like manner, the secondary triangular article is placed with its apexon line 80A and its X-axis and Z- axis edges touching points X and Erespectively and lines 88 and 89 are drawn from the apex to points X andE respectively. Then with the article held with its line of holes 47over line 88 a series of scaled dots 90 are made through these holes.Using a straight edge a series of parallel lines 91 which are parallelto line 80A are drawn to their intersections with line 79 thus depictingthe upper X-axis edge of the cube in the desired foreshortened size.

Having thus established the desired reference edges of the object inthree planes, a straight edge is employed to draw in the remainingX-axis edges; edges and 102; the remaining Y-axis edges 103 and 104; andthe remaining Z-axis edges 105 and 106.

As will be understood. if desired and without departing from theinvention, the left protractor 17 may also be equipped with a slot,scale and row of holes so that a similar construction of a trimetricprojection involving the tilting and revolving of an object in a reversedirection may be carried out. Also the right protractor may be equippedwith a vertical scale along its right hand edge.

Having described the use of the draftsmans aid in the construction ofthe difficult trimetric projection it will be apparent that it also issuitable for use with the much less difficult construction of thesimpler isometric and dimetric projections, such as would be involved inthe drawings of FIGS. 4 and 5 having angles as shown.

Obviously many modifications and variations of the present invention arepossible in the light of the above disclosure. It is therefore to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

What is claimed is:

l. A draftsmans aid comprising; a rigid, flat member having a straightedge along its lower portion and formed along its upper portion with acentral notch having symmetrically disposed upwardly inclined relativelyshort straight edges with right and left arcuate edges extendingdownwardly from the respective ends of said short edges, upwardlyextending right and left support arms affixed to said flat member alongits side portions and disposed in a plane above the plane of said flatmember, right and left protractors pivotally mounted upon the upper endsof said arms and adapted to revolve in the plane of said flat member andalong the arcuate edges thereof, said protractors being mounted inconfronting spaced relation in proximity to each other and having scaledstraight upper edges along which lines may be drawn representative ofthe settings of said protractors, and at least one of said protractorshaving a Yaxis slot therethrough located normally to the straight upperedge of the same protractor whereby markings may be made through saidslot upon a worksheet underlying said flat member and which arerepresentative of the selected setting of the slotequipped protractor.

2. A draftsmans aid as defined in claim 1 wherein at least one of saidprotractors includes a scaled straight exposed side edge normal to theupper edge of the same protractor.

3. A draftsman's aid as defined in claim 1 wherein said member is formedof transparent material and includes a visible reference line extendingdownwardly from the apex of said notch and normal to the lower straightedge of said member.

4. A draftsmans aid as defined in claim 1 including a scale along saidslot and an array of holes through the protractor adjacent said slot.

5. A draftsmans aid as defined in claim 1 wherein at least one of saidprotractors is pivotally mounted upon the arm by means of a cylindricalferrule containing a magnifying glass through which the worksheet may beobserved.

1. A draftsman''s aid comprising; a rigid, flat member having a straightedge along its lower portion and formed along its upper portion with acentral notch having symmetrically disposed upwardly inclined relativelyshort straight edges with right and left arcuate edges extendingdownwardly from the respective ends of said short edges, upwardlyextending right and left support arms affixed to said flat member alongits side portions and disposed in a plane above the plane of said flatmember, right and left protractors pivotally mounted upon the upper endsof said arms and adapted to revolve in the plane of said flat member andalong the arcuate edges thereof, said protractors being mounted inconfronting spaced relation in proximity to each other and having scaledstraight upper edges along which lines may be drawn representative ofthe settings of said protractors, and at least one of said protractorshaving a Y-axis slot therethrough located normally to the straight upperedge of the same protractor whereby markings may be made through saidslot upon a worksheet underlying said flat member and which aRerepresentative of the selected setting of the slot-equipped protractor.2. A draftsman''s aid as defined in claim 1 wherein at least one of saidprotractors includes a scaled straight exposed side edge normal to theupper edge of the same protractor.
 3. A draftsman''s aid as defined inclaim 1 wherein said member is formed of transparent material andincludes a visible reference line extending downwardly from the apex ofsaid notch and normal to the lower straight edge of said member.
 4. Adraftsman''s aid as defined in claim 1 including a scale along said slotand an array of holes through the protractor adjacent said slot.
 5. Adraftsman''s aid as defined in claim 1 wherein at least one of saidprotractors is pivotally mounted upon the arm by means of a cylindricalferrule containing a magnifying glass through which the worksheet may beobserved.